A level meter in a mold for continuous casting comprises a continuous casting mold, a stirrer comprising a continuous series of vertically elongated coils of wire surrounded by a core having pole pieces extending through the coils towards the mold and forming a multi-phase stirrer surrounding the mold, and means for metering or detecting the top level of the molten metal being cast into the mold so as to determine the rate at which the metal cast in the mold should be supplied.
Such a means can be provided by a radioactive source of radiation positioned outside of the mold to project a beam of radiation through the mold via one of its sides, and a radiation detector for the beam on the opposite side of the mold. When the metal in the mold intercepts the beam the level is detected and the rate at which the metal is supplied the mold can be increased or decreased to maintain a desired level of molten metal in the mold, keeping in mind that metal is continuously feeding from the mold in the form of a partially solidified continuously cast strand.
The purpose of the stirrer is to electromagnetically stir the molten metal in the mold as it progressively solidifies while passing downwardly through the mold which is cooled to solidify the metal at least at its part in contact with the mold. It may be desirable to stir the molten metal in the mold close to the upper surface of the metal, and for this the stirrer with its coils and pole pieces must extend from the mold's lower portion upwardly around the mold to the required level.
It is the purpose of the level meter to detect the melt level so as to maintain it safely close to the upper limit of the field of the stirrer, requiring the radiation source and detector to be positioned at least slightly below the top level of the electromagnetic stirrer. To accomodate this positioning it has been proposed that the coils and pole pieces of the stirrer be circumferentially separated so as to form gaps or spaces for the radiation source and detector.
The above gaps result in the coils and pole pieces of the stirrer being unsymmetrical and it has been found that the stirring action of the metal in the mold is not as effective as might be desired.
It is conceivable to design a stirrer with its coils juxtapositioned and its pole pieces symmetrically arranged without the gaps, by shortening the otherwise desirable vertical extent or height of the stirrer so that the radiation source and detector can be positioned at a level above the stirrer. This expedient prevents stirring of the metal near the top of the mold.